Such a load switch, as known from German patent 2,747,489 has for each of the phases to be switched respective auxiliary and main contact pairs which are moved with each switching one after the other. It further has for each phase to be switched two continuous main contact pairs, one contact pair of which conducts the main current in a stationary condition. The known load switch is formed as a cylinder; its housing is formed of cylindrical shells that carry the stationary main and auxiliary contacts. Arranged inside in sectors are the respective movable main and auxiliary contacts which are operated by a central switching shaft. Electrically parallel to the main contacts are respective load-free switching continuous current or continuous main contacts, the movable continuous main contacts being connected to the movable main contacts so as to be operated by them. It is known from German 1,930,719 that continuous main contacts connected to the respective main contacts are pivotal about a pin and biased by springs.
With the known load switch as described above the movable continuous main contacts are shifted together with the respective movable main contacts. Such a load switch is however principally intended only for carrying out such switching systems or switching sequences that are symmetrical, that is where independent of the switching direction and thus of the rotation direction of the switching shaft a fixed interval exists between the actuation of the main contacts and that of the respective continuous main contacts. In other words: with a symmetrical switching system with a reversed switching direction all the present main and auxiliary contacts are operated in the reversed order also.
Nonetheless so-called asymmetrical switching systems are known, for example from German 4,223,439 and WO 95/24724 which have electrical advantages and in particular are only logically usable when vacuum switches can be used as switching elements. With such asymmetrical switching systems the movement order of the individual main and auxiliary contacts is always the same; for example with the switching system known from WO 95/24724 in each switching direction the main contact moves before the auxiliary contact. The continuous main contacts that conduct the load current in the stationary condition must however open in any case even with asymmetrical switching systems as the first contact at the start of each load switching and as last contact at the end of each load switching. In other words, with such switching systems the actuation of the continuous main contacts remains symmetrical and that of the main and auxiliary contacts remains asymmetrical. This explains why the known load switch with a mechanical coupling of the continuous main contacts to the main contacts is not ideal for such switching systems.